U.S. Marine Corps recruit Caleb McCready, left, and recruit Mark Fiasconaro, both with Platoon 3060, Kilo Company, 3rd Recruit Training Battalion, flip over a set of double bars on an obstacle course, June 10, 2013, at Parris Island, S.C. The obstacle course was a combat conditioning tool used to build Marine Corps recruits' strength and stamina.
(U.S. Marine Corps photo by Lance Cpl. Caitlin Brink/Released). Original public domain image from Flickr